Roger Clemens’ life has officially gone from ERA and RBI to DNA and the FBI.

The FBI announced yesterday it has begun to investigate the 45-year-old former Yankees star for perjury. The announcement came one day after the leaders of a congressional committee wrote a referral to the Department of Justice asking for an investigation.

“The request to open an investigation on Roger Clemens has been turned over to the FBI, and will receive the appropriate investigative actions by the FBI’s Washington Field Office,” said Debbie Weierman, a spokesperson for the bureau.

Clemens faced off with his accuser and former trainer, Brian McNamee, on Feb. 13 in front of the House Committee on Oversight and Government Reform. The two told drastically different stories, leading the committee’s chairman Rep. Henry Waxman, D-Calif., and ranking minority member Rep. Tom Davis, R.-Va., to refer the matter to the Justice Department.

IRS agent Jeff Novitzky had begun a preliminary investigation into Clemens, gathering evidence from McNamee and planning a trip to Clemens’ hometown of Houston to begin digging. Now, a formal FBI field operation will begin. Novitzky is likely to lead the operation as part of a joint agreement between the IRS and FBI.

“I think even for a celebrity who is used to great scrutiny, nothing prepares you for being the target of an FBI field investigation,” said Jonathan Turley, a law professor at George Washington University. “It is highly disruptive to your life. They are going to look at every aspect of his professional, financial and personal life.

“I tell my clients who have been in this situation: They’re not hunting perjury, they’re hunting you.”

Clemens declined to speak with reporters again yesterday at Astros camp in Kissimmee, Fla. His lawyer, Rusty Hardin, reacted with ambivalence at the announcement.

“We’ve always expected they would open an investigation,” Hardin said in a statement. “They attended the Congressional hearing. So, what’s new?”

What’s new is Clemens’ life is about to be turned upside down and every inch is about to go under the microscope. Federal agents will begin interviewing anyone they believe has information on Clemens’ possible steroid use. A grand jury likely will be impaneled and subpoenas will be issued not only to people in Clemens’ life but to Clemens for medical, phone, financial and computer records.

The agents will scrutinize everything in Clemens’ life looking not only for proof of perjury but for any other crimes he may have committed to increase the likelihood of a guilty plea or conviction.

“These investigators will look at anything short of ripping a label off a mattress to charge him with,” Turley said.

The case likely will be assigned to the U.S. Attorney’s Office in Washington to oversee the case and bring a possible indictment. There will be no rush, though. As the government showed in the Barry Bonds case, they are happy to take their time and compile as much evidence as possible.

“They will probably cast as wide a net as possible and subpoena many people,” said Brad Simon, a criminal defense lawyer at Simon & Partners. “Many, many grand jury subpoenas get issued.”

That subpoena list could include many current and former Yankees: players Andy Pettitte and Mike Stanton and trainer Gene Monahan look like certainties, with former manager Joe Torre, general manager Brian Cashman, clubhouse staff, medical staff and players Gary Sheffield and Jason Giambi all possible.

A key witness may be Jose Canseco, who gave a sworn affidavit that Clemens never came to a party at his house in June 1998. Evidence has surfaced suggesting Clemens was there. Canseco already has been contacted by Novitzky but the two have not agreed to meet, according to Canseco’s attorney Robert Saunooke. He said Canseco is willing to talk to federal agents but they have to come to Canseco. He is unwilling to pay to travel in order to meet with them.

If the feds feel they have proof Clemens was at Canseco’s house, they may tell Canseco they will charge him with lying to federal agents as leverage to get him to become a cooperating witness.

The FBI announced yesterday it has opened an investigation into whether Roger Clemens committed perjury on Feb. 13 at a congressional hearing.

The Democratic staff of the House Committee on Oversight and Government Reform put together an 18-page memo that provides damning evidence against Clemens. Here’s a look at the seven things the committee questioned in the memo:

1. Clemens’ testimony that he has never used steroids or human growth hormone.

Brian McNamee testified he injected Clemens at least 38 times with either a steroid or HGH. McNamee’s testimony is backed up by that of Andy Pettitte and Chuck Knoblauch, who said McNamee was telling the truth about them.

2. Clemens’ testimony McNamee injected him with lidocaine

Testimony from doctors suggests it would be unusual for a team trainer to administer such a shot in the back, as Clemens claims, never mind a personal trainer like McNamee.

3. Clemens’ testimony team trainers gave him pain injections

Clemens told the committee “all trainers have given me shots.” This is contradicted by testimony from team trainers and doctors.

4. Clemens’ testimony he received many vitamin B12 injections

The committee went through medical records dating back to 1995 and found only one B12 injection, coming in 1998.

5. Clemens’ testimony he never discussed HGH with McNamee

Later when asked about his wife’s use of HGH, Clemens said he had an angry conversation with McNamee about giving her the shot.

6. Clemens’ testimony he was not at a party at Jose Canseco’s house in 1998

The testimony of Clemens’ nanny, along with a photo that has surfaced of a neighbor posing with Clemens that day, have erased doubt he was there.

7. Clemens’ testimony he was “never told” former Sen. George Mitchell had made a request to interview him as part of his steroids probe

The committee staff says it was “unlikely” Clemens’ agents would make a decision for him not to talk to Mitchell without running it by Clemens first. Pettitte, who has the same agents, said he was informed by them Mitchell wanted to talk to him.